The invention relates to pumps and other apparatus in wells, and more particularly to vertical positioners and torque arrestors for submersible water pumps.
Submersible centrifugal pumps powered by electric motors are commonly suspended at the end of the length of a pipe within a well. A problem common to small diameter wells in many locations is that particulate debris is present on the bottom of the well, either from its original use or with the passage of time. It is therefore necessary that a submersible pump be located some distance above debris, to avoid entrainment of it into the pump intake with consequent damage of the impellers. Normally, this is accomplished by first measuring the depth of the well and then providing only sufficient pipe to suspend the pump the desired distance above the debris. However, if the debris is particularly light it is difficult to ascertain its depth at the bottom of the well. On the other hand it is undesirable to suspend a pump too great a distance above any debris since it is advantageous to be able to "draw down" the maximum water in the well when demand exceeds the infiltration capacity of the well.
Another problem in applications such as domestic water supplies results from periodic on-off pump cycling. When the pump motor is started there is a force between the armature and field, with the result that a torsional moment is imparted to the pump housing. The pump is characteristically fitted rather closely in the well; e.g. a four inch diameter pump may be in a six inch well bore. Thus, there is a tendency for the suspended pump to both rotate and move laterally, twisting the suspending pipe and causing contact with the well bore. This effect is especially present when pumps are suspended in a well from long thermoplastic pipes.
The lateral movement and contact of the pump with the well bore can cause abrasion and eventual failure of the pump housing. Repetitive torsion may cause pipe failure and loosening of associated pipe fittings. Therefore, means to prevent such damage are required. A conventional device presently used is comprised of a collar or multiplicity of fingers extending from the pump or the pipe line near the pump. The device, often made of a resilient material such as a thermoplastic or rubber, is adjusted to the nominal diameter of the well prior to lowering of the pump into the well. Thus, the device has a tendency to rub along the sides of the well bore, thereby impeding the lowering or raising of the pump. Further, the device must be adjusted to pass by the narrowest point in the well, and if the well bore varies in diameter the device may not fully prevent movement when the pump is at its working location in the well. Still another problem results when a conventional torque arrestor is fitted to the pipe just above the pump; in many pumps the direction of rotation is such that there is a tendency for loosening of the fitting which adapts the pipe to the pump discharge.
Accordingly, there is a need for an improved means for positively locating and fixing the position of a submersible pump within a well bore, both laterally and vertically.